Multi-domain test and measurement instrument

ABSTRACT

A test and measurement instrument including a time domain channel configured to process a first input signal for analysis in a time domain; a frequency domain channel configured to process a second input signal for analysis in a frequency domain; and an acquisition system coupled to the time domain channel and the frequency domain channel. The acquisition system is configured to acquire data from the time domain channel and the frequency domain channel. Time domain and frequency domain data can be time aligned.

BACKGROUND

This disclosure relates to test and measurement instruments, inparticular to test and measurement instruments with inputs optimized forboth time domain and frequency domain analysis.

Electronic devices can operate with signals that can be represented inmultiple domains. That is, an electronic device can have signals thatare customarily defined mathematically in the time domain, such asdigital control signals, data, and transmitter/receiver control signals,and signals that are most often defined in the frequency domain, such asmodulated RF and/or optical carriers.

For example, a frequency-hopping spread-spectrum based device can changeits carrier frequency according to a pseudorandom number. Thispseudorandom number can be encoded in a control signal of a transmittingdevice. Since the pseudorandom number changes over time, the controlsignal encoding the pseudo random number is typically analyzed in thetime domain. However, the resulting changes to the carrier are changesin frequency that are typically analyzed in the frequency domain.

Accordingly, signals can exist within a device or system that must beanalyzed in both the time domain and the frequency domain. As describedabove, aspects of such signals can be linked together, such as thepseudorandom number and the carrier frequency. However, test andmeasurement instruments are typically designed for analysis in only onedomain. For example, an oscilloscope can measure signals in the timedomain and a spectrum analyzer can measure signals in the frequencydomain. Such measuring instruments are not time-aligned. Thus, analysisof multi-domain devices described above is difficult.

Some test and measurement instruments have some multi-domain analysiscapability. For example, an oscilloscope can provide a discrete Fouriertransform (DFT) function to display a frequency spectrum of an inputsignal. However, a DFT of a digitized time domain signal is limited bythe nature of a DFT. That is, to obtain a small frequency step, i.e. afine resolution in the frequency domain, a long time span is necessaryin the time domain. Similarly, to acquire data for a wide frequencyspan, a high sample rate is needed. Thus, fine resolution of a modulatedcarrier at a higher frequency requires both a high sample rate and along time span, requiring a large acquisition memory, which is expensiveor unavailable in an oscilloscope.

Furthermore, time alignment of signals in the time domain and signals inthe frequency domain can be affected by sample rate and acquisitiontime. For example, a higher time precision in the time domain requires ahigher sample rate. However, with a given fixed memory size, the highersample rate limits the time span and thus the size of a frequency stepin the frequency domain. In other words, the frequency domain analysisprecision is limited by the time domain analysis precision

Since test and measurement instruments with such multi-domain capabilitytypically have acquisition parameters such as sample rate and recordlength for multiple channels linked together, simultaneous analysis inboth the time domain and the frequency domain can be difficult. That is,precision in one domain can be mutually exclusive with precision in theother.

SUMMARY

An embodiment includes a test and measurement instrument including atime domain channel configured to process a first input signal foranalysis in a time domain; a frequency domain channel configured toprocess a second input signal for analysis in a frequency domain; and anacquisition system coupled to the time domain channel and the frequencydomain channel. The acquisition system is configured to acquire datafrom the time domain channel and the frequency domain channelsubstantially simultaneously.

An embodiment includes frequency shifting a first signal; digitizing thefrequency shifted first signal; storing the digitized frequency shiftedfirst signal in a memory; digitizing a second signal; and storing thedigitized second signal in the memory.

An embodiment includes a test and measurement instrument including atime domain channel configured to process a first input signal foranalysis in a time domain; a frequency domain channel configured toprocess a second input signal for analysis in a frequency domain; and acontroller coupled to the time domain channel and the frequency domainchannel and configured to control acquisition parameters of the timedomain channel and the frequency domain channel such that theacquisition parameters of the time domain channel and the frequencydomain channel are different.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a test and measurement instrument having atime domain channel and a frequency domain channel according to anembodiment.

FIG. 2 is a block diagram of an example of frequency domain channel inthe test and measurement instrument of FIG. 1.

FIG. 3 is a block diagram of a test and measurement instrument having atime domain channel and a frequency domain channel coupled to a singleinput according to an embodiment

FIG. 4 is a block diagram of an example of the test and measurementinstrument of FIG. 3.

FIG. 5 is a block diagram of a test and measurement instrument havingdifferent acquisition parameters for multiple channels according to anembodiment.

FIG. 6 is a block diagram of a test and measurement instrument havingtrigger system that can trigger an acquisition from a time domainchannel and/or a frequency domain channel according to an embodiment.

FIG. 7 is a block diagram of a test and measurement instrument having atime domain channel and a frequency domain channel according to anotherembodiment.

FIG. 8 is a block diagram of an example of the digital downconverter inthe test and measurement instrument of FIG. 7.

DETAILED DESCRIPTION

Embodiments include test and measurement instruments and techniqueswhere signals can be analyzed in multiple domains. For example, controlsignals which determine when events happen can be analyzed in the timedomain. These control signals often control a frequency event, such as achange in a carrier frequency. In an embodiment, acquisition of signalsto analyze the two events can be optimized for time domain analysis, forfrequency domain analysis, and for time aligned analysis between thedomains.

FIG. 1 is a block diagram of a test and measurement instrument having atime domain channel and a frequency domain channel according to anembodiment. In this embodiment, the instrument 10 includes a time domainchannel 12 configured to receive a first input signal 18, and afrequency domain channel 14 configured to receive a second input signal20. An acquisition system 16 is coupled to the time domain channel 12and the frequency domain channel 14, and is configured to acquire datafrom the time domain channel and the frequency domain channel.

The time domain channel 12 can be configured to sample the first inputsignal 18 for analysis in the time domain. For example, the time domainchannel 12 can include digitizers such as multi-bit analog to digitalconverters, comparators for sensing discrete levels, or the like. Thetime domain channel 12 can include other circuitry, such as amplifiers,input protection, or other conditioning circuitry. The time domainchannel 12 can include other digital processing circuitry, such asmemories, decimators, or the like. Accordingly, the output signal 26 canbe the digitized version of the input signal 18 in the time domain.

In an embodiment, the time domain channel 12 can include circuitry thatis optimized for acquisition of a signal for analysis in the timedomain. For example, a signal suited to time domain analysis can be acontrol signal, a data signal, or the like. Such signals can havefrequency components from DC to a maximum frequency, such as 1 GHz, 26.5GHz, or the like. Accordingly, the time domain channel 12 can includeamplifiers, attenuators, and other circuitry that cover the entirebandwidth from DC to the maximum frequency.

The frequency domain channel 14 can be configured to process the secondinput signal 20 differently than the time domain channel 12. Inparticular, the frequency domain channel 14 can be configured to processthe second input signal 20 for analysis in the frequency domain. Forexample, as will be described in further detail below, the second inputsignal 20 can be frequency shifted to a different frequency range. Inparticular, the second input signal 20 can be downconverted to a lowerfrequency range. That is, the input signal 20 has been frequencyshifted. In an embodiment, this frequency shifted signal can be theoutput signal 28.

This frequency shifting is an example of a difference in processing ofan input signal by the time domain channel 12 and the frequency domainchannel 14. In addition, in an embodiment, the frequency domain channel14 can include attenuators, filters, amplifiers, or the like that can beoptimized for those signals that require frequency-domain representationand analysis. For example, an amplifier in the frequency domain channel14 can be configured to have a lower noise figure and a lower maximuminput level than an amplifier in the time domain channel 12. In anotherexample, the amplifier can have a different frequency range. That is, anamplifier in the time domain channel 12 can have a frequency range of DCto 26.5 GHz. The amplifier can be optimized for amplifying signalsthroughout the frequency range. However, when analyzing a high frequencysignal in the frequency domain and, in particular, when analyzing asignal that was downconverted in the frequency domain components that donot operate across an entire frequency range from DC to a maximumfrequency can be used. For example, if a signal of interest has afrequency range centered at 15 GHz, an amplifier with a frequency rangefrom 10 GHz to 20 GHz can be used. Such an amplifier can have betterperformance over its frequency range than an amplifier spanning thelarger frequency range from DC to 26.5 GHz.

Similarly, the frequency domain channel 14 can include other componentsthat have different bandwidths, input ranges, noise figures, or the likethat would otherwise be used in the time domain channel 12. That is,amplifiers, mixers, local oscillators, attenuators, filters, switches,or the like in the frequency domain channel 14 can be selected to havefeatures that would degrade and/or eliminate the full bandwidth of atime domain channel 14.

Accordingly, due to the frequency shifting described above, effects ofthe different components described above, or the like from the frequencydomain channel 14, the output signal 28 can be a signal that isprocessed more appropriately for frequency domain analysis than ifprocessed in a time domain channel 12. Furthermore, as will be describedin further detail below, the input signal 20 has been processedaccording to frequency domain related acquisition parameters that can benot only appropriate to the frequency range, resolution bandwidth, orthe like that is of interest, but may be also be different from theacquisition parameters of the time domain channel 12. That is, not onlycan the frequency domain channel 14 have different components than thetime domain channel 12, but the frequency domain channel 14 and the timedomain channel 12 can be operated differently, for example, by havingdifferent sample rates, record lengths, or the like. Thus, each of thefrequency domain channel 14 and the time domain channel 12 can beoptimized for corresponding analysis of the acquired signals in thefrequency domain and time domain, respectively.

The acquisition system 16 can include a variety of circuitry. Forexample, the acquisition system can include digitizers, decimators,filters, memories, or the like. The acquisition system 16 can be coupledto the time domain channel and the frequency domain channel andconfigured to acquire data from the time domain channel and thefrequency domain channel. For example, the time domain channel 12 can beconfigured to filter, scale, or otherwise condition the output signal 26to be in an appropriate range for a digitizer of the acquisition system.Similarly the frequency domain channel 14 can also be configured tocondition the signal for a digitizer of the acquisition system 16,albeit differently than the time domain channel 12 as described above.

FIG. 2 is a block diagram of an example of frequency domain channel inthe test and measurement instrument of FIG. 1. In this example, thefrequency domain channel 14 includes an attenuator 30, a filter 31, amixer 32, a local oscillator 33, and an IF filter 34. The input signal20 is received by the attenuator 30. The attenuator 30 can be a fixedattenuator, variable attenuator, switched attenuator, or the like. Theattenuated signal is filtered by filter 31. In an embodiment, the filter31 can be selected as desired for the appropriate input frequency range.For example, the filter 31 can be a low-pass filter, a band-pass filter,a high pass filter, or the like depending on the particular frequencyrange of interest, the oscillator 33 frequency, or the like.

The filtered signal can be downconverted to an IF range using the mixer32 and local oscillator 33. An IF filter 34 can filter the IF signalbefore it is available as an output signal 24. In this embodiment, theoutput signal 24 can be the frequency domain channel 14 output signal 28of FIG. 1, available to be acquired by the acquisition system 16.

In an embodiment, the output signal 24 represents the input signal 20after downconversion to the IF frequency range. This IF signal can befurther processed or acquired in the acquisition system 16 asillustrated in FIG. 1. For example, as will be described in furtherdetail below, the IF signal can be converted in to in-phase (I) andquadrature phase (Q) signals, transformed using a Fourier transform, orthe like.

In another embodiment, the frequency domain channel 14 can include adigitizer 35, and a digital filter 36. The digitizer 35 can beconfigured to digitize the output IF signal 24. The digital filter 36can be applied to reduce artifacts, provide a windowing function, or thelike to the digitized IF signal. Accordingly, a digitized IF signal 25can be available as the frequency domain channel 14 output signal 28 ofFIG. 1, to be acquired by the acquisition system 16.

In yet another embodiment, the frequency domain channel 14 can include amemory 37 and a processor configured to perform a Fourier transform 38such as a fast Fourier transform (FFT), discrete Fourier transform(DFT), chirp-Z transform, or the like on a segment of the digitized IFsignal 25. At this point the digitized IF signal 25 can be transformed,changing its mathematical representation from a function of time to afunction of frequency, represented by transformed signal 27. Although aFourier transform 38 has been given as an example, other transforms,such as a Laplace transform, a Hilbert transform, or the like can besubstituted as desired. Regardless, the transformed IF signal 27 can beavailable as the frequency domain channel 14 output signal 28 of FIG. 1,to be acquired by the acquisition system 16.

Accordingly, the frequency domain channel 14 output signal 28 can take avariety of forms suitable to allow analysis of the input signal 20 inthe frequency domain. The various components, processing, and the likecan be divided between the frequency domain channel 14 and theacquisition system 16 as desired. However, regardless of form, theoutput signal 28 can be processed by components that can be selectedand/or tuned for the frequency range of interest. Regardless of the formof the frequency domain channel 14 output signal 28, the acquired data22 including data from the time domain channel 12 and the frequencydomain channel 14 can be available for further processing, display,analysis in the respective domain, or the like.

In an embodiment, the acquisition system 16 can be configured to acquiresubstantially time aligned versions of the output signal 26 and theoutput signal 28. For example, the output signals 26 and 28 can bestored in an acquisition memory of the acquisition system 16. As will bedescribed in further detail below, the acquisitions of the outputsignals 26 and 28 can be performed in response to the same trigger.Accordingly, as the output signal 26 can be acquired with the timedomain channel 12 optimized for time domain analysis and the outputsignal 28 can be acquired with the frequency domain channel 12 optimizedfor frequency domain analysis, substantially time aligned time andfrequency domain analyses can be performed without sacrificing theoptimization of acquisition for one analysis domain over another.

Although a selection of components of the frequency domain channel 14has been illustrated, other components, such as amplifiers, switches,decimators, limiters, or the like can be present and/or replaceillustrated components.

Referring back to FIG. 1, in an embodiment, the time domain channel 12,the frequency domain channel 14, and the acquisition system 16 can besubstantially encapsulated in a housing 24. For example, the instrument10 can include a case. The time domain channel 12 can include an inputconnector on a front panel, such as a BNC connector, a multi-channelconnector, or the like. The frequency domain channel 14 can have aconnector suitable for higher frequencies, such as an SMA, N, 2.92 mm,or other high performance connector. That is, the frequency domainchannel 14 can include a connector that is optimized higher frequencyperformance.

The housing 24 can include a common display, keys, knobs, dials, orother user interfaces. Although common aspects of the user interface cancontrol different aspects of time domain and frequency domain signals,different interfaces can be provided to access the different functions.For example, one button may cause a common knob to control the timebase. Another button may cause the common knob to control the centerfrequency.

In an embodiment, the time domain channel 12 and the frequency domainchannel 14 can have different operational frequency ranges. The timedomain channel 12 can have a first operational frequency range. Forexample, the time domain channel 12 can be DC coupled. That is, the timedomain channel 12 can be used to acquire DC signals and/or basebandsignals with frequency components down to DC. In addition, the timedomain channel 12 can have a relatively low upper frequency limit. Forexample, a time domain channel 12 can have a 1 GHz bandwidth. Thus, thetime domain channel 12 can be configured to have an input frequencyrange from DC to 1 GHz.

However, the frequency domain channel 14 can be configured to have adifferent input frequency range. For example, as illustrated in theexample of FIG. 2, the frequency domain channel 14 can be configured todownconvert the input signal 20 to a lower IF frequency range. Thus, theoperational input frequency range of the frequency domain channel 14 canbe configured to be different from the time domain channel 12. Forexample, the input frequency range of the frequency domain channel couldbe up to 26.5 GHz. That is, the various filters 31, 34, 36, or the like,can affect the operational input bandwidth.

Furthermore, the components selected for the frequency domain channel 14can be selected to optimize the associated frequency ranges, rather thanthen entire input frequency range. For example, the components can beselected for an optimum sensitivity, dynamic range, noise level, or thelike for a particular frequency range. In contrast, in an embodiment,the time domain channel 12 can be optimized for its entire frequencyrange. That is, the time domain channel 12 can be configured to expect asignal anywhere within its entire bandwidth. However, the frequencydomain channel 14 can be configured to select a particular frequencyrange of interest. Moreover, the frequency domain channel 14 can beconfigured to acquire signals outside of the bandwidth of the timedomain channel. Accordingly, the frequency domain channel 14 can beoptimized for that frequency range.

FIG. 3 is a block diagram of a test and measurement instrument having atime domain channel and a frequency domain channel coupled to a singleinput according to an embodiment. In this embodiment, the time domainchannel 12 and the frequency domain channel 14 can each be configured toreceive the same input signal 42. For example, a splitter, switch,selector, or other signal routing device 44 can be used to route theinput signal 42. Accordingly, in one configuration, only the time domainchannel 12 receives the input signal 42. In another configuration, onlythe frequency domain channel 14 receives the input signal 42. In yetanother configuration, both the time domain channel 12 and the frequencydomain channel 14 can receive the input signal 42.

In an embodiment, each of the time domain channel 12 and the frequencydomain channel 14 can have its own digitizer. Accordingly, the outputsignal 26 and 28 can be digital signals that have been digitized in achannel optimized for analysis in a respective time domain and frequencydomain. In another embodiment, as described above, digitizers can bepart of the acquisition system 16. Still, the output signals 26 and 28can be analog signals that have been processed such that they areoptimized for acquisition and analysis in the respective domains.

FIG. 4 is a block diagram of an example of the test and measurementinstrument of FIG. 3. In this embodiment, the instrument 50 includes acommon input 44 configured to receive an input signal 42, adownconverter 57, a selector 53, and a digitizer 55. The downconverter57 can include a mixer 51 and a local oscillator 52. Other components,such as filters, amplifiers, attenuators, or the like are notillustrated for clarity. The downconverter 57 can output a downconvertedversion 58 of the input signal 42.

Both the input signal 42 and the downconverted signal 58 are availableto the selector 53. Accordingly, on a single input 44, circuitry thatcan be optimized for analysis in the frequency domain, such as thedownconverter 57 and/or other associated amplifiers filters, or thelike, can be added to a single channel. However, common circuitry, suchas the digitizer 55 can be used for both directly digitizing the inputsignal 42 as well as the downconverted signal 58 to be used in timedomain and frequency domain analysis.

For example, the digitizer 55 can be capable of digitizing at a 1 GS/ssample rate. Accordingly, the time domain path 43 can have acorresponding maximum input frequency, such as 500 MHz. In contrast, thefrequency domain path 45 can include components that allow for asubstantially higher maximum frequency range. For example, thedownconverter 57 can be configured to downconvert signals havingfrequencies up to 26.5 GHz. However, the IF bandwidth of thedownconverted signal 58 can be 500 MHz. Thus, the same digitizer 55 andother common circuitry can still be used to digitize both basebanddigital signals and downconverted signals.

As will be described in further detail below, the digitizer 55 can beconfigured to operate at a different sample rate when performingfrequency domain analysis than when performing time domain analysis. Forexample, in response to the selection signal 54, the digitizer 55 can beconfigured to select a sample rate appropriate to the incoming signal.That is, in an embodiment, a high sample rate can be used foracquisition of a signal for time domain analysis; however, a lowersample rate appropriate to the downconverted signal 58 can be used foracquisition of a signal for frequency domain analysis.

Thus, the same input can be configurable to provide both a signal 26optimized for time domain analysis and a signal 28 optimized frequencydomain analysis. As illustrated in FIG. 3, the same input signal can beacquired and analyzed substantially simultaneously in the time domainand the frequency domain. However, as illustrated in the embodiment ofFIG. 4, the signal path for the acquired signal can be selected from oneoptimized for time domain analysis and another optimized for frequencydomain analysis.

FIG. 5 is a block diagram of a test and measurement instrument havingdifferent acquisition parameters for multiple channels according to anembodiment. In this embodiment, the instrument 60 includes a time domainchannel 63 and a frequency domain channel 67, each of which is coupledto an acquisition system 70 similar to FIG. 1 described above. Acontroller 69 is coupled to the time domain channel 63 and the frequencydomain channel 67. The controller 14 can be any variety of circuitry.For example, the controller 14 can include analog and digital circuitry.The controller 14 can include general purpose processors, digital signalprocessors, application specific integrated circuits, programmable gatearrays, or the like. The controller 14 can also include appropriatecircuitry to interface with the time domain channel 63, the frequencydomain channel 67, and the acquisition system 70.

The controller 69 can be configured to control the acquisitionparameters of the time domain channel 63 and the frequency domainchannel 67. In particular, the controller 69 can be configured tocontrol the acquisition parameters such that the acquisition parameterscan be different. In this example, the controller 69 can be configuredto control the sample rates 64 and 68 of the respective digitizers 62and 66. The sample rate 64 and the sample rate 68 are configurable suchthat the sample rate 64 and the sample rate 68 can be different.Accordingly, the digitized time domain data 71 and the digitizedfrequency domain data 73 can have different lengths.

The independence of the sample clocks allows for independent control oftime domain and frequency domain parameters. For example, to acquire atime domain signal, the sample rate can be selected to exceed thehighest frequency component of interest in the time domain signal by afactor of two. If the time domain signal has frequency components at 1GHz, a sample rate of 2 GS/s or above can be used. If the frequencydomain channel is locked to the same sample rate, then, when using aDFT, the frequency step size or an associated resolution bandwidth ofthe frequency domain data 73 directly drives the number of samples, orthe time span. As a result, the resolution bandwidth is limited by theavailable acquisition memory size. Alternately, the sample rate of thetime domain channel 63 will be limited in order to realize a narrowresolution bandwidth on the frequency domain channel 67.

In contrast, if the sample rates can be different, a sample rateappropriate to the desired aspects of the frequency domain data 73 canbe selected. For example, if the input signal 20 is downconverted asdescribed herein, a lower sample rate corresponding to the desiredfrequency span can be used. That is, if the carrier was at 1 GHz and themodulation occupied 20 MHz, the downconverted signal could occupy 20 MHzplus and additional margin for filtering, sampling, or the like.Assuming that such a sample rate is 50 MS/s, 1/40^(th) of theacquisition memory would be needed for the same time span and hence, thesame frequency step size.

The above scenarios are merely examples that illustrate where differentsample rates can be used. Regardless of the specific application, thedifferent sample rates allow the selection to be made particular to thegiven channel, input signal, and domain of interest.

The sample rates described above for the time domain channel 63 and thefrequency domain channel 67 can be different, but not necessarilyindependent. For example, the different sample rates can be phase lockedto a common, lower frequency clock. However, independence here can meanindependently controllable. Moreover, although separate sample rates 64and 68 have been described, the associated oscillators, clocks, or thelike can be substantially synchronized with a common circuit for theinstrument 60.

Furthermore, although a sample rate has been used as an example of anacquisition parameter that could be different between the time domainchannel 63 and the frequency domain channel 67, other acquisitionparameters can be controlled by the controller 69 to be different. Forexample, the controller 69 can be configured to control the acquisitionsystem 70 such that the acquisition periods, record lengths, or the likeassociated with the time domain channel 63 and frequency domain channel67 are different. In another example, the controller 69 can beconfigured to adjust components in the respective channels, such asfilter bandwidths, filter center frequencies, attenuator settings, orthe like. As a result, the acquisition parameters for the time domainchannel 63 and frequency domain channel 67 can each be controlled tooptimize the channel for the acquisition of the associated input signalsuch that the associated input signal is optimized for analysis indifferent domains.

FIG. 6 is a block diagram of a test and measurement instrument havingtrigger system that can trigger an acquisition from a time domainchannel and/or a frequency domain channel according to an embodiment. Inthis embodiment, the instrument 90 includes an acquisition system 92.The acquisition system 92 can include a triggering system 94. Thetriggering system can be coupled to the time domain channel 12 and thefrequency domain channel 14. Accordingly, an acquisition of theacquisition system 92 can be triggered in response to time domainsignals, frequency domain signals, a combination of such signals, or thelike.

As the same event or combination of events can be used to triggeracquisitions in both the frequency and time domains, the acquiredsignals can be time aligned to a higher degree. For example, theacquired data can be as time aligned as two input channels of anoscilloscope, i.e. substantially aligned on a per sample basis. Thus,when examining an event in one domain, the corresponding, substantiallycontemporaneous signals in another domain can be analyzed. As usedherein, substantially contemporaneous and/or time aligned can include atime accuracy that is limited by a lowest sample rate of time alignedchannels.

Furthermore, the common triggering can result in cross-domaintriggering. For example, the acquisition system 92 can be configured toidentify an event in the time domain signal 18. In response anacquisition of the frequency domain signal 20 can be triggered. In thisexample, the time domain signal 18 need not have been acquired. Forexample, a signal turning a transmitter on, i.e. a time domain controlsignal, can be used to trigger an acquisition of the transmitted signal.The transmitted signal can be analyzed in the frequency domain.

Similarly, a frequency domain event can be used to trigger a time domainacquisition. For example, a received RF signal can be monitored untilthe frequency range changes to a particular frequency range, such as oneof the ranges associated with a frequency-hopping signal. An acquisitionof the demodulated data in the receiver can be acquired for analysis inresponse to the appearance of the RF signal in the frequency range ofinterest.

Although an event in one domain has been described as used to trigger anacquisition for analysis in another domain, the same event could be usedto trigger an acquisition for analysis in any or all domains.Furthermore, events from different domains can be combined together. Forexample, a frequency domain glitch or other spurious signal can becombined with a control signal indicating that the signal of interestshould be within the frequency span with the glitch. That is, signalsassociated with a receiver can be acquired in response to both afrequency domain anomaly and a control signal of the receiver indicatingthat it is expecting a signal in the associated frequency range.Although particular examples of signals, characteristics of signals,combination of events, or the like have been described above, any eventsfrom any signals can be used and/or combined as desired to trigger anacquisition.

FIG. 7 is a block diagram of a test and measurement instrument having atime domain channel and a frequency domain channel according to anotherembodiment. In this embodiment, the instrument 110 includes a timedomain channel 129 and a frequency domain channel 127. Each includesrespective digitizers 112 and 114. The frequency domain channel includesan analog downconverter 125 configured to receive the input signal 20.The digitizer 114 is configured to digitize the downconverted signalfrom the analog downconverter 127.

In an embodiment, the digitized signals from the digitizer 112 and 114could be stored in a memory 116. Subsequent processing, as will bedescribed below, could be performed as desired on the stored digitizedsignals in the memory 116.

Regardless of whether the digitized signals are stored in the memory116, further processing can be performed. For example, the digitizedsignal 118 can be further processed by time domain processing 122. Forexample, signal conditioning, filtering, decimation or the like can beapplied to the time domain signal 118. The resulting processed timedomain signal 126 can be stored in the memory 134.

The frequency domain channel 127 also includes a digital downconverter124. The digital downconverter 124 can be configured to convert thedigitized downconverted signal 120 into an in-phase (I) and quadraturephase (Q) representation. This can be accomplished through an additionaldownconversion processes. Accordingly, the downconverted signal 128 caninclude both the in-phase and quadrature phase representations of theinput signal 20. In another example, the I/Q signals can be convertedinto other signals, such as amplitude, phase, frequency, or the like.Furthermore, the I/Q signals can be demodulated to capture theunderlying symbols, bits, or other data. In another example, atransformation such as an FFT can be applied. Any such processing can beperformed to generate any of these signals or other signals to be storedin the memory 134.

FIG. 8 is a block diagram of an example of the digital downconverter inthe test and measurement instrument of FIG. 7. In this embodiment, thedigitized signal 120 is input to both an in-phase path 148 and aquadrature phase path 150. Each path is configured to receive a signalfrom a local oscillator 142; however, the quadrature phase path 150 isconfigured to receive a signal that is 90 degrees out of phase with thesignal received by the in-phase path 148.

Each path 148 and 150 is configured to mix the input signal 120 with thecorresponding signal from the local oscillator 142. Thus, in-phasesignal 144 and quadrature phase signal 146 are created. Additionalfiltering and/or decimation can be applied to the signals 144 and 146 asdesired. As described above with respect to FIG. 7, these signals can bestored in the memory 134, further processed, or the like. In particular,signals 144 and 146 can be a complex-number representation of thedigitized signal 120. For example, in-phase signal 144 can represent areal part of the digitized signal 120 and quadrature phase signal 146can represent the imaginary part of the digitized signal 120. Such acomplex-number representation can be used to calculate various otherrepresentations of the digitized signal 120, such as phase, frequency,encoded data, or the like.

Although a DFT has been described above in connection with the frequencydomain processing, any Fourier transform or other transforming functionscan be used as desired.

Although various signals have been described above as downconverted infrequency, such signals can be upconverted as desired into anappropriate IF frequency range. For example, frequencies below an IFfrequency range can be upconverted into the IF frequency range. Suchupconversion and downconversion can collectively be referred to asfrequency shifting

Although particular embodiments have been described, it will beappreciated that the principles of the invention are not limited tothose embodiments. Variations and modifications may be made withoutdeparting from the principles of the invention as set forth in thefollowing claims.

The invention claimed is:
 1. A test and measurement instrument,comprising: a time domain channel configured to process a first inputsignal for analysis in a time domain; a frequency domain channelconfigured to process a second input signal for analysis in a frequencydomain; and an acquisition system coupled to the time domain channel andthe frequency domain channel and configured to acquire data from thetime domain channel and the frequency domain channel, wherein the timedomain channel and the frequency domain channel are not used to processthe same signal sequentially.
 2. The test and measurement instrument ofclaim 1, further comprising: a trigger system coupled to the time domainchannel and the frequency domain channel, and configurable to trigger anacquisition of the acquisition system in response to at least one of anevent from the time domain channel and an event from the frequencydomain channel.
 3. The test and measurement instrument of claim 1,wherein the acquisition system is configured to time align anacquisition of the time domain channel with an acquisition of thefrequency domain channel.
 4. The test and measurement system of claim 1,further comprising: a controller coupled to the time domain channel andthe frequency domain channel and configured to control acquisitionparameters of the time domain channel and the frequency domain channelsuch that the acquisition parameters of the time domain channel and thefrequency domain channel are different.
 5. The test and measurementsystem of claim 4, wherein: the time domain channel is configured tosample at a first sample rate; the frequency domain channel isconfigured to sample at a second sample rate; and the controller isconfigured to set the first sample rate and the second sample rate to bedifferent.
 6. The test and measurement system of claim 1, furthercomprising: an input port; wherein the input port is configured toreceive an input signal and provide the input signal to the time domainchannel and the frequency domain channel.
 7. The test and measurementsystem of claim 6, wherein the time domain channel and the frequencydomain channel are configured to process the input signalcontemporaneously.
 8. The test and measurement system of claim 1,further comprising: an acquisition memory; wherein: the frequency domainchannel further comprises: an in-phase path coupled to the acquisitionmemory; and a quadrature-phase path coupled to the acquisition memory;and the time domain channel is coupled to the acquisition memory.
 9. Thetest and measurement system of claim 1, further comprising: a housing;wherein the time domain channel, the frequency domain channel, and theacquisition system are substantially encapsulated in the housing. 10.The test and measurement system of claim 1, wherein: the time domainchannel has a first frequency range; the frequency domain channel has asecond frequency range; and the first frequency range is different fromthe second frequency range.
 11. The test and measurement system of claim1, further comprising: an input port coupled to the frequency domainchannel and the time domain channel; a selector configured to receive anoutput of the frequency domain channel and an output of the time domainchannel; and a digitizer configured to digitize an output of theselector.
 12. A test and measurement instrument, comprising: a timedomain channel configured to process a first input signal for analysisin a time domain; a frequency domain channel configured to process asecond input signal for analysis in a frequency domain; and a controllercoupled to the time domain channel and the frequency domain channel andconfigured to control acquisition parameters of the time domain channeland the frequency domain channel such that the acquisition parameters ofthe time domain channel and the frequency domain channel are different.13. The test and measurement instrument of claim 12, wherein the timedomain channel is configured to sample at a first sample rate; thefrequency domain channel is configured to sample at a second samplerate; and the controller is configured to set the first sample rate andthe second sample rate to be different.
 14. The test and measurementinstrument of claim 12, further comprising: an acquisition systemcoupled to the time domain channel and the frequency domain channel andconfigured to acquire data from the time domain channel and thefrequency domain channel; wherein: the acquisition system is configuredto acquire the data from the time domain channel over a first timeperiod and acquire the data from the frequency domain channel over asecond time period; and the controller is configured to set the firsttime period and the second time period to be different.
 15. The test andmeasurement instrument of claim 12, wherein the time domain channel isconfigured to have a first bandwidth; the frequency domain channel isconfigured to have a second bandwidth; and the controller is configuredto set the first bandwidth and the second bandwidth to be different.